In particular, yet not restrictive manner, the disclosure concerns recycling of sheet shaped panels comprising wood fibers, especially laminates floorings. However, the disclosure is as well applicable to building panels in general. The present disclosure is particularly suitable for use in floating floors, which are formed of floorboards which are made up of one or more preferably moisture-proof upper layers of decorative laminate or decorative plastic material, an intermediate core of wood-fiber-based material or plastic material and preferably a lower balancing layer on the rear side of the core.
The following description of known techniques, problems of known systems and objects and features of the disclosure will therefore, as a non-restrictive example, be aimed above all at this field of application and in particular laminate flooring. However, it should be emphasized that the disclosure can be used in optional floorboards where the floorboards preferably have a core and at least one surface layer. The disclosure can thus also be applicable to, for instance, floors with one or more surface layers of wood, plastic material, flexible fibers such as needle felt or combinations of different materials, for instance wood, plastic, cork, rubber or other materials that are used as surface layers in floors.
Laminate flooring usually comprises a core of a 6-12 mm fiberboard, a 0.2-0.8 mm thick upper decorative surface layer of laminate and a 0.1-0.6 mm thick lower balancing layer of laminate, plastic, paper or like material. The surface layer provides appearance and durability to the floorboards. The core provides stability, and the balancing layer keeps the board plane when the relative humidity (RH) varies during the year. The disclosure generally relates to the field of recycling of wood fiber based panels especially laminate floorings. The disclosure provides new sheet materials and methods to produce such materials.
The floorboards are usually laid floating, i.e. without gluing, on an existing sub floor which does not have to be completely smooth or plane. Traditional hard floorboards in floating flooring of this type have usually been joined by means of glued tongue-and-groove joints.
In addition to such traditional floors, which are joined by means of glued tongue-and-groove joints, floorboards have recently been developed which do not require the use of glue and instead are joined mechanically by means of so-called mechanical joint systems. These systems comprise locking means, which lock the boards horizontally and/or vertically.
The main advantages of floating floors with mechanical joint systems are that they can easily and quickly laid by various combinations of inward angling, snapping-in and displacement along the joint edge. The floorboards can also easily be taken up again and used once more at a different location.
The most common core material is fiberboard with high density and good stability usually called HDF—High Density Fiberboard. Sometimes also MDF—Medium Density Fiberboard—is used as core. As a rule, these core materials are of high quality.
HDF is produced as follows: Roundwood such as for example pine, larch or spruce are reduced to wood chips and then broken down into fibres in a refiner. The fibres are thereafter mixed with a thermosetting binder and then subjected to high pressure and temperature in a press. Fibers are bonded to each other with the cured binder.